1. Field of the Invention
The invention generally relates to rotary driven cylindrical cutters and scarifiers for use in earth-working, mining, or other in situ disintegration of hard materials. The invention is particularly directed to a tool holder for such a machine.
2. Background of the Invention
In general, roadway mining or planing equipment includes a rotary driven cylindrical comminuting drum which acts to scarify and to mine the top portion of the asphaltic road surface in situ. The rotary driven drum includes flighting on the drum which acts to collect and move the mined material toward the center of the drum where it can be removed. Often the mined material is then remixed with additional bituminous material and thereafter re-deposited as a newly formed smooth asphaltic surface. The rotary driven drums can also be used in other types of mining including subterranean extraction of desirable minerals and ores.
In some prior art devices of this type, the flighting is itself formed from a plurality of cutting bit support members which are connected to the curved surface of the cutting drum by bolts which pass from the upper surface of the flighting downward into the drum to engage threaded openings in the drum. Alternatively, the cutting bit support members can be welded to the drum or to the flighting.
A plurality of flight blocks can be arranged end-to-end so as to form a substantially continuous helical flighting. The top surface of the helical flighting is generally elevated above the curved surface of the drum. The flight blocks can include angled openings into which conventional tool holders are received. Each tool holder has a recess to receive a cutting tool.
In use, the tool holders may vibrate and otherwise move within the flight blocks. Particularly in the presence of abrasive debris from the roadway mining operation, the vibration and movement of the tool holders can act to enlarge the slot within the flight block receiving the tool holder to such an extent that the tool holder is no longer retained. Additionally, the presence of dust and debris that is being churned up by the cutting tool itself can get pushed into the flight block, between the wall of the slot and the tool holder. This debris causes added and accelerated wear on the tool holder and flight block.
When the tool holder is no longer held securely in the flight block, it then becomes necessary to remove the old flight block, usually with the aid of a cutting torch, and to weld a new flight block in its place. Again, this repair job is difficult to do in the field and still achieve accurate alignment of the flight block on the flighting section. Misalignment of the flight block results in undesirable lateral forces on a new cutting tool which in turn results in very fast wear and ultimate failure of the replaced parts.
The vibration induced wear can also occur between the tool holders and the cutting tool itself. Some rotational movement of the cutting tool may be desirable to permit the cutting tool to suffer even wear. Any rotational movement of the tool can cause wear of the part holding the tool, whether the tool holder or any intermediate sleeve. It is desirable to retain the cutting tool in the tool holder so long as the cutting surface of the cutting tool remains satisfactory to perform the desired cutting action. If a cutting tool experiences too much wear it may be ejected from or drop from the tool holder. If the tool holder experiences too much wear in surfaces confronting the cutting tool, the tool holder may not be able to retain even a new cutting tool, thus mandating the replacement of the tool holder. Thus, it is desirable to accommodate some measure of wear between the cutting tool and the tool holder while minimizing the wear on the tool holder itself.
Thus, there remains a need for a tool holder that can be used with standard flight blocks, and will resist the intrusion of debris between the tool holder and the cutting tool and will retain the cutting tool for a longer time. There remains a further need for a tool holder that can accommodate or compensate for some measure of wear of the cutting tool in relation to the tool holder.